By my reckoning, with the helmet of Eminent Destruction and the Adept perk, at level 100 Destruction, it'll cost 231 Magicka. (Compare to 82 if single cast.)

By the way, while I'm already posting, I'll just take this opportunity to restate how much I love this build. It's straight up criminal that it hasn't even hit 50 likes yet.

And I disagree with the people who are advising you to cut stuff, Kaiser. Only cut something if you think its presence detracts from the build. Personally, I don't think there's anything here that does detract, so unless you feel you could be more concise by rewriting sections, I suggest leaving it as is.

@Emmanouil: Yeah, Whirlwind Cloak is quite costly. That's where potions come in handy - Potions of Fortify Magicka are your best friend. If you have to, switch one of the enchantments for a magicka or destruction enchant. If you grabbed the Atronach Stone you should have 200 magicka, putting a few points in magicka might not be terrible either.

Also, I didn't pick up the Bloodskal Blade until much later (22-25ish). If you have trouble with Dragons then by all means go ahead and get Dragonrend - I didn't get it but that doesn't mean everyone has to stop at the same place! Again, totally glad you enjoy the build and if there's anything else please tell me! 

@Teccam: Thanks for the quick fact on the magicka cost as well as your support! I wasn't planning on cutting this build - maybe try to make a later build shorter but I feel that everything in this build has a place and I'm glad someone else does too! 

I opened up most battles with a rune until 40 as well as training it when ever I had some extra cash. It didn't take too long to get to 40. Using runes to open combat is great and I did it for most battles after whirlwind cloak for a fall-back.

I believe the Dawnguard Rune Hammer levels Destruction just as quickly as rune spells. Might be a good backup to the Bloodskal Blade (or a fitting substitute before you are skilled enough to pick up the blade).

Great build Kaiser! easy +1

Nice build, but I think you shouldn't care about the civil war. Why not? Imperials are Thalmor-ass-licking dogs while Stormcloaks would never accept an Altmer, even if you're an outcast. Anyway, +1. If build includes lycantropy, it instantly earns half of my like :D :D